Biology-introduction

• Transport


  Movement of substances within an organism
• What’s the need for transport

  Carry required substances to body parts

  Remove metabolic wastes from the body
• Why is it necessary for an elaborate transport system in large multi-cellular organisms?

  They have a complex structure where cells are far from each other hence diffusion alone cannot meet the demand for supply and removal of substances
• Vascular bundles comprise of and give the meaning of your answer


  Xylem-transport water and mineral salts

  Phloem-Transport dissolved food substances
• Simple plants such as mosses and liverworts transport substances by:

  Diffusion,Osmosis,Active transport
• Higher plants have a specialized transport system known as

  vascular bundles
• The main functions of the roots are:

  Anchorage,Absorption,Storage,Gaseous exchange
• The outermost layer of the root is the

  piliferous layer
• Root hairs are thin-walled because/why?

  To shorten distance for absorption of water and mineral salts
• Root hairs are numerous and elongated because/why?

  Increased surface area for absorption of water and mineral salts
• Define Piliferous layer

  A special epidermis of young roots that give rise to root hairs
• The cortex have loosely packed thin-walled cells because/why?

  To allow water molecules to reach the vascular bundles
• Root cap-

  Consists of simple parenchyma cells that protect the root tip
• Piliferous layer-


  A special epidermis of young roots whose cells form/give rise to root hairs
• Cortex-


  Consists of loosely packed parenchyma cells(acts as a storage tissue)
• Pericycle-


  A single layer of cells below the endodermis that give rise to lateral roots

  lateral roots-smaller roots that emerge horizontally from the taproot(main root)
• Vascular bundle-


  Consists of the xylem and phloem
• Endodermis-


  A single layer of cells which surround the vascular bundle and controls the amount of water and mineral salts entering the vascular bundle
• Root hairs-

  They arise from the epidermal cells and provide a large surface area for absorption of water and mineral salts
• The root is divided into two MAIN roots namely:

  Monocot roots and Dicot roots
• Diferences between monot and dicot roots are?

  Monocot roots have a fibrous root system, while dicot roots have a taproot system.
• Root hairs are long because?

  To provide a large surface area for absorption of water and mineral salts
• Root hairs are thin-walled because/why?

  To reduce the distance hence faster diffusion of water and mineral salts
• Characteristics of dicotyledons

  Xylem is star shaped(polygonal)

  Pith is absent

  Xylem and Phloem are limited/few

  Pericycle give rise to lateral roots,cork and vascular cambium
• Characteristics of monocotyledons

  Xylem is oval-shaped or round

  Pith is present

  Numerous Phloem and Xylem

  Pericycle mainly give rise to the lateral roots
• Epidermis is also known as?

  Poliferous
• Similarities between dicotyledons and monocotyledons roots

  Both are used for anchorage and absorption of water and mineral salts

  Both have root hair,epidermis,pericycle,endodermis, vascular bundles, Xylem and Phloem

  Both store foo/store organs
• Main functions of the stem are?

  Support and exposure of leaves and flowers to the environment

  Conducting manufactured food from leaves to other parts of the plant

  Conducting water and mineral salts
• What is the difference between vascular bundles in monocotyledons and dicotyledon?

  Monocotyledons have scattered vascular bundles, while dicotyledons have vascular bundles arranged in a ring.
• Vascular bundles are continuous from

  Root to stem and leaves
• Epidermis forms:

  A single layer of cells enclosing other tissues
• Outer walls of the cells have a waxy cuticle because/why?

  Prevent excessive loss of water
• The cortex consists of:

  collenchyma,parenchyma,schlerenchyma cells
• Collenchyma-


  Next to the epidermis and has thickened walls at the corners which strengthen the stem
• Parenchyma-


  Cells are irregular in shape,thin-walled and loosely arranged hence creating intercellular(they are packing tissues and food storage areas)
• Sclerenchyma-

  Cells are closely connected to the vascular bundles(these cells are thickened by deposition of lignin and they provide support to plants)
• Pith-


  Is the central region having parenchyma cells
• Why does the root hair cell have a higher osmotic pressure than the surrounding soil water solution?

  It has solutes in the vacuole
• Water moved into the root hair cells along a concentration gradient by/through?

  Osmosis
• What makes the sap in the root hair cell to have a lower osmotic pressure than the surrounding cells?

  Water moving into the root hair cells by osmosis along a concentration gradient